"A complainant alerted Ofcom to offensive language in this program when their 6-year-old child was watching," the agency said in a report. It noted five instances of the words "f—k" or "f—king" during the episode, 11 scenes where someone said "shit" and one scene in which someone used the word "bitch."

The show aired at 8 p.m., ahead of what is known as the 9 p.m. "watershed" in Britain, after which edgier material can air.

"The most offensive language must not be broadcast before the watershed," according to British rules. "Offensive language must not be broadcast before the watershed … unless it is justified by the context. In any event, frequent use of such language must be avoided before the watershed."

Discovery "extended its unreserved apologies to the viewer for any distress caused by the offensive language in this case," Ofcom said. "It added that it had investigated this incident and had discovered "[r]egrettably" the program had been broadcast as a result of human error."

Discovery told the U.K. regulator that the postwatershed version of the show had been incorrectly labeled as being suitable for a prewatershed time slot.

Discovery vowed to ensure that "this kind of error is not repeated," according to the regulator's report. It added that it was also reviewing all other episodes of the season and has introduced further changes to its compliance processes as a result.

Ofcom in its conclusion noted that "Discovery accepted immediately that this program breached rules 1.14 and 1.16, apologized and took various steps after the broadcast to ensure it was not shown again before it was re-edited and to improve compliance going forward."